1. Field of the Invention
The present invention relates to an electrolytic capacitor allowing reduction of equivalent series resistance.
2. Description of the Background Art
Recently, there have been demands for electric circuits that are smaller in size and adapted for high-frequency applications. With this trend, capacitors of lower impedance become necessary. Particularly, in designing a circuit for driving a CPU (Central Processing unit) of a computer, a switching power supply circuit and the like, absorption of high-frequency noise and ripple current is necessary, and therefore, a capacitor of which equivalent series resistance (ESR) can be made low has been required.
FIG. 27 is a perspective view showing a structure of a conventional aluminum-rolled solid electrolytic capacitor. Referring to FIG. 27, the conventional aluminum-rolled solid electrolytic capacitor 100 includes a chemically processed anode foil 110, a cathode foil 120, a separator sheet 130, a securing tape 140, lead tab terminals 160, 170, an anode lead 180 and a cathode lead 190.
Chemically processed anode foil 110, cathode foil 120 and separator sheet 130 are rolled such that separator sheet 130 is positioned between chemically processed anode foil 110 and cathode foil 120. Securing tape 140 tapes ends of the rolled chemically processed anode foil 110, cathode foil 120 and separator sheet 130, and thus, a capacitor element 150 is formed.
Lead tab terminal 160 is connected to chemically processed anode foil 110 to protrude from an end surface of capacitor element 150, while lead tab terminal 170 is connected to cathode foil 120 to protrude from the end surface of capacitor element 150. Anode lead 180 is connected to lead tab terminal 160 and cathode lead 190 is connected to lead tab terminal 170.
Conventionally, as a method of reducing equivalent series resistance, connecting two leads to each of the chemically processed anode foil and cathode foil has been known (Japanese Patent Laying-Open No. 2004-179621). FIG. 28 shows a method of connecting two anode leads to the chemically processed anode foil. Referring to FIG. 28, two lead tab terminals 160a and 160b are connected, spaced by a prescribed distance from each other, to chemically processed anode foil 110. Two anode leads 180a and 180b are respectively connected to lead tab terminals 160a and 160b. 
Two cathode leads are connected to cathode foil 120 in the similar manner as two anode leads 180a and 180b are connected to chemically processed anode foil 110.
FIG. 29 is another illustration showing a method of connecting two anode leads to the chemically processed anode foil. Referring to FIG. 29, a lead tab terminal 160c is connected to chemically processed anode foil 110, and two anode leads 180a and 180b are connected, spaced by a prescribed distance from each other, to lead tab terminal 160c. Two cathode leads are connected to cathode foil 120 in the similar manner as two anode leads 180a and 180b are connected to chemically processed anode foil 110.
In the conventional aluminum-rolled solid electrolytic capacitor, equivalent series resistance can be reduced to about 2.0 mΩ.
As described above, it has been known that equivalent series resistance can be reduced by connecting two leads to each of the chemically processed anode foil and the cathode foil.
According to the conventional method of reducing equivalent series resistance, however, a plurality of anode leads are connected to the chemically processed anode foil and a plurality of cathode leads are connected to the cathode foil, and therefore, it has been difficult to fabricate an aluminum-rolled electrolytic capacitor while maintaining constant the positions for connecting the plurality of anode leads to the chemically processed anode foil and the positions for connecting the plurality of cathode leads to the cathode foil.
Consequently, it has been difficult to fabricate an aluminum electrolytic capacitor with low ESR in a stable manner. Specifically, dependent on the position of connection between the anode lead and the chemically processed anode foil and the position of connection between the cathode lead and the cathode foil, the equivalent series resistance varies (Japanese Patent Laying-Open No. 2005-203402), and therefore, it is difficult to connect the plurality of anode leads and a plurality of cathode leads to the chemically processed anode foil and the cathode foil every time at the same positions to fabricate aluminum electrolytic capacitors having approximately the same equivalent series resistance.